MOSS LANDING - The placid waters of Elkhorn Slough are host to the things that make Monterey Bay a natural treasure: gliding pelicans, twittering sandpipers, lounging sea lions and frolicking harbor seals. But all is not well here: a serial killer may be at work.

The suspect: an adolescent male known by the name "Morgan." His apparent method: molesting his young victims before drowning them.

Details about Morgan are sketchy: Separated from or abandoned by his mother soon after birth, he was raised by rehabilitation specialists before graduating to life on his own. His motives remain a mystery. As for his physical description, tourists who have seen him in and around the slough describe him as frisky, whiskery and curiously "cute."

Morgan is a sea otter. He was one of the star graduates of the prestigious Monterey Bay Aquarium Sea Otter Rescue and Conservation program until he hit puberty and somehow went awry. Now his exploits are posing a serious ethical quandary for the scientists and officials charged with protecting Monterey Bay's extraordinary ecosystem.

His reported victims are young harbor seals. Information gathered by the aquarium, a boat captain who leads daily tourist expeditions into the slough, and researchers at Moss Landing Marine Laboratories suggests he plays too rough with the seals and ultimately may shove their snouts underwater so long that they drown or die of shock trauma.

"It's hard to believe, I know," said Andy Johnson, director of the Monterey Bay Aquarium's Sea Otter Research and Conservation Program. "Harbor seals are not without defenses. They have teeth, they have claws, they can hold their breath underwater for a long time - typically longer than sea otters. It's amazing that they succumb to him."

The evidence against Morgan is circumstantial - no one has witnessed an actual seal killing. Unlike many rehabitated otters, he does not carry a radio transmitter and is identifiable only by his distinct flipper tag. But researchers report he has been observed assuming a mating position with a seal and then been seen roughing it up. Soon thereafter, Morgan has been spotted floating with the dead seal in his grip or nonchalantly grooming himself alongside its body.

About a dozen unconfirmed victims have been recovered this summer.

"We've had a lot more seal pups turning up dead in Elkhorn Slough this year than ever before," said seal expert Dr. Jim Harvey, an Associate Professor at Moss Landing's labs, which train students from the California State University system.

The labs have performed necropsies on several seals. Harvey noted that quite a few appeared to have been in excellent health, with no signs that they were malnourished or afflicted by parasites. In other words, their deaths were sudden and suspect.

"If this were reversed and a seal was attacking sea otters, there's no doubt that animal would already be out of the wild by now," Harvey said.

But because Morgan is an otter, he enjoys a kind of diplomatic immunity.

Fur traders had culled the southern sea otter population to the brink of extinction off the Big Sur Coast before the International Fur Seal Treaty of 1911 intervened. Now sea otters are classified as "threatened" animals under the Endangered Species Act.

Thanks to preservation efforts and the unique otter research, rescue and rehabilitation efforts of the aquarium, the official year 2000 count indicates there are 2,317 otters today. Previously, a stranded sea otter pup had little hope of survival. But the aquarium's ambitious program has taken in some 189 otters, providing round-the-clock care. Caregivers tend to and groom rescued pups, feeding them a baby otter formula that includes clams, squid, half-and-half, fish oil and vitamins.

Later they escort the pups into Monterey Bay for supervised swims and start to break bonds so that the otters can make a better transition into the wild. Otters that demonstrate survival skills are outfitted with tracking gear and then returned to the natural world.

Morgan's caregivers had high hopes that he would mature into a prolific breeder.

"It really is a roll of the dice with every animal we release," Johnson said. Some have been success stories. None have acted out like Morgan, behavior Johnson concedes is "aberrant."

Those otters, which lived off San Nicolas in the Channel Islands, appear never to have gotten aggressive enough to kill a seal.

"For a while we thought (Morgan) might just be going through a phase on the road to sexual maturity, and that a few harbor seal pups might die and then he would grow out of it," Johnson said. Sea otters typically hang out in bachelor groups, he said, and "we were kind of hoping the local dominant male would just kick his butt and he would shape up."

Instead Morgan, approaching his 5th birthday, appears to be moving up from pup victims, targeting larger juvenile seals. Among his unconfirmed victims: two seals being tracked in research projects by Moss Landing Marine Labs.

While otters evoke predictable "awws" from tourists and inspire tons of cuddly stuffed animals bearing their likeness, they are wild animals that can be quite ferocious. Their jaws are powerful, designed to crack shellfish, and full-grown males weigh in at an average of 65 pounds. As for their sex drive, pontoon boat captain Yohn Gideon gazed at two otters in the throes and observed with a shrug that an otter's mating season is "pretty much the same as a

human's."

And they play rough enough that female otters routinely emerge from mating with bloodied noses.

Given those circumstances, what now to do with Morgan?

"I think we're going to try to act pretty quickly," said Sanders of the U.S. Fish and Wildlife Service. "We've given (the aquarium) verbal OK to consider moving the animal, depending on the destination. We're waiting for written documentation of the incidents, but I think there's enough evidence of drowning and injury to seals to merit moving him."

The aquarium team is exploring a less protected locale with fewer vulnerable harbor seals. It's a place where Morgan may have to devote more of his energies to self-preservation. "Usually sea otters don't have a lot of spare time on their hands," Johnson said. "Maybe this one's getting into trouble because he has too much free time."

Relocation may not be a panacea. Experts predict Morgan probably will try to return to Elkhorn Slough. Aquarium officials say they're prepared to try repeated relocations.

Sanders said federal authorities likely will insist he be outfitted with a radio transmitter to make that easier. And although no one is

suggesting the aquarium's rehabilitation techniques are to blame for Morgan's behavior, Sanders said aquarium researchers feel responsibility for the animal and are willing to keep close track of him.

If Morgan ultimately violates the terms of his probation, odds are he'll be destined for display in a public aquarium, museum or aquatic park. &lt;